Proteins. R. R. O. O. H. H. N. C. C. N. C. C. H. H. OH. H. H. OH. Draw an explanation of how the above amino acids will join together. You should circle what will be removed and then draw the product .
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Draw an explanation of how the above amino acids will join together.
You should circle what will be removed and then draw the product.
Circle the bond formed and name it. What is this type of reaction called
Extension – The bond is broken by a hydrolysis reaction draw a diagram to show how this happens
Proteins are made of amino acids which have a central carbon atom with three different chemical groups attached:
Carboxylic acid group
Amino acids are so called because they have both amino groups (-NH2) and acidic groups (-COOH).
Amino acids are made of the five elements C H O N S
There are 20 different R-groups and so 20 different amino acids. This means that there are many, many different proteins with differing numbers and combinations of amino acids
Joining amino acids involves, again, a condensation reaction. The bond formed is called a peptide bond
Two amino acids form a dipeptide, many amino acids form a polypeptide. In a polypeptide, one end is still the amino group and the other end the acidic group.
The same type of reaction, hydrolysis, is again involved in breaking down (or hydrolysing) proteins. This can be achieved in the presence of protease enzyme or by boiling with dilute acid.
This can also be shown using the three letter abbreviations for each amino acid:
Gly – Pro – His – Leu – Tyr – Ser – Trp – Asp - Lys
This is the folding that then occurs, being held together by hydrogen bonds between the amino and carboxyl groups.
The two main types of secondary structure are the alpha helix and the beta pleat.
In the alpha helix the polypeptide chain is wound round to form a helix that is held together by many hydrogen bonds. In the beta pleat, the polypeptide chain zig-zags back and forward, once again held together by hydrogen bonds
This is the three dimensional structure formed by the folding up of the whole chain, with every proteins properties and functions being related to this. E.g. the unique shape of an enzymes active site is due to its tertiary structure. Three kinds of bond hold this structure together:
Hydrogen bonds,which are relatively weak
Ionic bonds between the R-groups, which are quite strong
Sulphur bridges between the sulphur containing amino acids, which are strong
This structure is found only in those proteins that contain more than one polypeptide chain, and simply means how the different chains are arranged together e.g. haemoglobin
The final 3-D shape of a protein can be described as globular or fibrous
GLOBULAR: most proteins, soluble, have biochemical roles e.g. enzymes, receptors, hormones
FIBROUS: look like “ropes”, are insoluble and have structural functions e.g. Collagen, keratin
Proteins can be identified with blue Biuret Reagent (copper sulphate and sodium hydroxide).
Blue Biuret reagent turns lilac in the presence of protein